charcoal gray vs charcoal grey

charcoal gray and charcoal grey both are nouns.

Word	Noun	Adjective	Verb	Adverb
charcoal gray	Yes	No	No	No
charcoal grey	Yes	No	No	No

As nouns, charcoal gray and charcoal grey are synonyms defined as:

Other synonyms of charcoal gray include charcoal, oxford gray, oxford grey.

charcoal gray (noun)	charcoal grey (noun)
a very dark grey color	a very dark grey color